1. Field
The embodiments relate to a thin film transistor substrate and a method for fabricating the same.
2. Description of the Related Art
A thin film transistor substrate is used as a substrate of an active liquid crystal display, an active organic electro luminescence (EL) display or the like which actively displays an image for each of pixels arranged in a matrix.
The liquid crystal display uses a thin film transistor as a switching device for controlling an image signal being transmitted to an electrode. The organic electro luminescence (EL) display includes a driving thin film transistor and a switching thin film transistor which supply current for light emission to each pixel.
The thin film transistor substrate includes a plurality of gate lines and data lines arranged horizontally and vertically to define a plurality of pixel regions, thin film transistors as switching devices formed at intersections of the gate lines and the data lines, and pixel electrodes formed in the pixel regions.
In an active layer of the thin film transistor, if an ON voltage equal to or greater than a threshold voltage is applied to a gate electrode, a channel is formed, and, if an OFF voltage is applied to the gate electrode, the channel vanishes to cut off the current between the source electrode and the drain electrode.
A high ON voltage is applied to the gate electrode in order to sufficiently form a channel between the source electrode and the drain electrode, and a high OFF voltage is applied to the gate electrode in order to completely extinguish the formed channel. If a high ON voltage is not applied to the gate electrode, the channel is not sufficiently formed such that the current does not flow smoothly. If a high OFF voltage is not applied to the gate electrode, leakage current is generated.